Excellent location! Only a few steps from Ratchathewi BTS station, and you can also easily walk to BTS Siam / MBK (max. 10 minutes). Beware that the location shown on AirBnB is misleading! The place is actually right next to VIE Hotel, very easy to find, and the Maid picked me up from there. Pan will give you the correct info anyhow when you check with her, just a heads up!
You'll be staying on the top floor of the house, no elevator. It's easy to walk the stairs, was not an issue at all, just keep in mind if you have heavy luggage. The room is basic, but clean, and has aircon. Bathroom is outside, no hot water, but anyhow in the heat it's refreshing :)
I really enjoyed my stay, thanks to the excellent location and hospitality!